1. Field of the Invention
The present invention relates to a method for inspecting liquid crystal display (LCD) panels, and more particularly, to a method for inspecting the cell process of LCD panels.
2. Description of the Prior Art
Liquid crystal display (LCD) devices are widely employed in various applications such as portable information electronics (e.g., laptop computers and personal digital assistants), home consumer electronics (e.g., LCD TVs), aerospace apparatus, and medical electronic devices due to their merits of light weight, low power consumption, and no radiation.
An LCD panel is one of the most important components of the LCD device. The LCD panel typically comprises a color filter (CF) substrate, a thin-film transistor (TFT) substrate (or referred to as array substrate), and liquid crystal material layer sandwiched between the CF substrate and the TFT substrate.
Generally, the LCD fabrication process can be divided into three processes: an array process, a cell process, and a module assembly process. Briefly, the array process forms a TFT array on a glass substrate to produce a TFT substrate. The cell process bonds a CF substrate with the TFT substrate, and then fills liquid crystal material between the CF substrate and the TFT substrate to produce a panel module. The module assembly process combines the panel module with a backlight module, driving circuits, an outer case, and other components. In practice, the yield rates of the array process and the module assembly process are higher than that of the cell process, so that the cell process becomes a critical process of the LCD fabrication.
In the cell process, a conventional inspection method of the LCD panel is to emit a light from outside the TFT substrate to pass the TFT substrate and the LC layer so as to illuminate the CF substrate. Since the CF substrate has a black matrix (BM) formed with high reflectance metal material such as chromium (Cr), the incident light will be reflected back to the TFT substrate. Thus, in the cell process, an inspection apparatus (or an inspection staff) can observe the inside pattern of the LCD panel through the reflected light and inspect the associated parameters of the cell process such as the seal width, inhaled volume of UV-epoxy in the LC slit, etc.
In order to conform to environmental protection rules such as the European Commission Directive on Waste Electrical and Electronic Equipment (WEEE), the metal material of the black matrix formed on the CF substrate will be progressively replaced with organic materials such as resin. However, when the resin BM is adopted in the CF substrate, the aforementioned inspection method becomes unable to be put into practice. This is because the resin BM is low reflectance material and may absorb the incident light. Consequently, the inspection apparatus or staff has difficulty inspecting the inside pattern of the LCD panel through the reflected light so that it is unable to measure the associated parameters of the cell process.